1. Field of the Invention
This invention relates to an optical scanning apparatus and an image displaying apparatus having the same, and is suitable, for example, for an image displaying apparatus of a scanning type for scanning a surface to be scanned with a light beam optically modulated on the basis of image information from light source means to thereby display and observe a two-dimensional image, or directly direct a two-dimensional image to an eyeball and observe it.
2. Related Background Art
There is known an image displaying apparatus for scanning an observer's retina by the use of optical scanning means capable of two-dimensionally scanning with a beam optically modulated on the basis of image information from light source means to thereby display an image (for example, U.S. Pat. No. 5,467,104). U.S. Pat. No. 5,467,104 discloses the technique of scanning with red, blue and green beams in a two-dimensional direction, i.e., a horizontal direction and a vertical direction, by scanning means, and directly forming a two-dimensional image on the retina through an optical system.
Such an image displaying technique need not use a displaying element in which a plurality of pixels are formed in accordance with necessary resolution as in an image displaying apparatus using a two-dimensional or one-dimensional image displaying element, since an image is displayed by scanning with a beam, and the image displaying technique has the feature that a faulty pixel does not occur in principle.
In realizing an image displaying apparatus using such scanning means, a micro electro mechanical system (hereinafter referred to as the MEMS technique) manufactured by a semiconductor manufacturing process is known as optical scanning means (for example, U.S. Pat. No. 5,606,447 and Japanese Patent Application Laid-Open No. H08-334723). The optical scanning means manufactured by the MEMS technique is compact and light in weight and can operate at a high speed, and such features are suitable for the image displaying apparatus. There is also known the MEMS technique of two-dimensional scanning means for a head-mounted-display apparatus (for example, SPIE Conference #4407, 19 (June 2001) Wafer scale packaging for a MEMS video scanner).
In the optical scanning means by these MEMS techniques, a surface reflecting light is resonated by a torsion bar or the like and with the torsion due to the resonance the light reflecting surface is inclined and deflect the light incident on the reflecting surface to scan with the light.
On the other hand, in an image displaying apparatus for enlarging and displaying, in combination with an optical system, an image displayed by scanning with a beam optically modulated by an optical scanning apparatus using a galvano mirror on the basis of image information, there is known an image displaying apparatus in which the alignment of the optical scanning apparatus and the optical system is effected highly accurately (for example, Japanese Patent No. 3219465).
As the optical scanning apparatuses manufactured by the conventional MEMS technique, there have been proposed one in which a scanning surface (reflecting surface) for deflecting a light beam is vacuum-sealed and one which is driven under the atmospheric pressure. In the optical scanning apparatus wherein the scanning surface is vacuum-sealed, a scanning device is packaged and therefore the problem of dust or the like does not readily arise, but yet the cost becomes high due to an increase in the assembling steps.
On the other hand, in the scanning device driven under the atmospheric pressure, a coil as driving means and a magnet are disposed near the scanning surface and therefore, a magnetic material such as iron powder has tended to be attracted by the magnetic force thereof or minute dust has tended to adhere to a member such as a reflecting mirror constituting the scanning device by static electricity.
There is a method of disposing a protective member in order to reduce the adherence of dust before light is incident on the scanning device, but this method suffers from the optical problem that there is produced stray light or the like having nothing to do with image display which has been reflected by or transmitted through the protective member. Also, by disposing the protective member, a limitation occurs to the disposition of the scanning device. Besides these, there is the problem that the provision of the protective member leads to an increase in the number of parts, which in turn leads to the complication of the construction of the scanning device.